package bash

import (
	"fmt"
	"runtime"
	"sort"
	"strings"
)

type shellState struct {
	cwd      string
	username string
	hostname string
	fs       *filesystem
}

type commandResult struct {
	output string
	exit   bool
}

func dispatch(state *shellState, line string) commandResult {
	fields := strings.Fields(line)
	if len(fields) == 0 {
		return commandResult{}
	}

	cmd := fields[0]
	args := fields[1:]

	switch cmd {
	case "pwd":
		return commandResult{output: state.cwd}
	case "whoami":
		return commandResult{output: state.username}
	case "hostname":
		return commandResult{output: state.hostname}
	case "id":
		return cmdID(state)
	case "uname":
		return cmdUname(state, args)
	case "ls":
		return cmdLs(state, args)
	case "cd":
		return cmdCd(state, args)
	case "cat":
		return cmdCat(state, args)
	case "exit", "logout":
		return commandResult{exit: true}
	default:
		return commandResult{output: fmt.Sprintf("%s: command not found", cmd)}
	}
}

func cmdID(state *shellState) commandResult {
	return commandResult{
		output: fmt.Sprintf("uid=0(%s) gid=0(%s) groups=0(%s)", state.username, state.username, state.username),
	}
}

func cmdUname(state *shellState, args []string) commandResult {
	if len(args) > 0 && args[0] == "-a" {
		return commandResult{
			output: fmt.Sprintf("Linux %s 5.15.0-89-generic #99-Ubuntu SMP Mon Oct 30 20:42:41 UTC 2023 %s GNU/Linux", state.hostname, runtime.GOARCH),
		}
	}
	return commandResult{output: "Linux"}
}

func cmdLs(state *shellState, args []string) commandResult {
	target := state.cwd
	if len(args) > 0 {
		target = resolvePath(state.cwd, args[0])
	}

	names, err := state.fs.list(target)
	if err != nil {
		return commandResult{output: err.Error()}
	}

	sort.Strings(names)
	return commandResult{output: strings.Join(names, "  ")}
}

func cmdCd(state *shellState, args []string) commandResult {
	target := "/root"
	if len(args) > 0 {
		target = resolvePath(state.cwd, args[0])
	}

	if !state.fs.exists(target) {
		return commandResult{output: fmt.Sprintf("bash: cd: %s: No such file or directory", args[0])}
	}
	if !state.fs.isDirectory(target) {
		return commandResult{output: fmt.Sprintf("bash: cd: %s: Not a directory", args[0])}
	}

	state.cwd = target
	return commandResult{}
}

func cmdCat(state *shellState, args []string) commandResult {
	if len(args) == 0 {
		return commandResult{}
	}

	var parts []string
	for _, arg := range args {
		p := resolvePath(state.cwd, arg)
		content, err := state.fs.read(p)
		if err != nil {
			parts = append(parts, err.Error())
		} else {
			parts = append(parts, strings.TrimRight(content, "\n"))
		}
	}

	return commandResult{output: strings.Join(parts, "\n")}
}